The present invention relates to a cylinder block for a multi-cylinder internal combustion engine, and more specifically to technique for sensing knocking accurately.
Knocking is undesired vibrations of gases in a combustion engine resulting from spontaneous ignition of unburnt gas mixture in a terminal portion of the combustion chamber. Violent knocking causes unpleasant vibrations and noise, and incurs a decrease in the output power and deterioration in fuel consumption due to energy loss. To avoid the problem of knocking, an engine of some type is provided with a control system for performing a control operation such as retardation of ignition timing in accordance with a signal from a knock sensor mounted in a knock sensor mounting boss of a cylinder block.
A Published Japanese Patent Application Publication No. H06(1994)-193502 shows a knock sensor mounting boss for a multi-cylinder engine. One side wall of a cylinder block is formed with a rib connecting projection parts of vertically extending oil drain holes, so as to transmit knocking vibrations to the knock sensor mounting boss.